1. Field of the Invention
The present invention relates to a multiple-input multiple-output (MIMO) communication system including deterministic processing.
2. Description of the Related Art
Multiple-input multiple-output (MIMO) communication systems are known for diversity, coding gain, and capacity improvement. In MIMO systems, transmit and receive diversity can be achieved if perfect knowledge of the channel gains is available at the transmitter and the receiver, respectively. In the transmitter, a transmit weight vector can be obtained in order to maximize a performance metric like signal-to-noise ratio (SNR) with the perfect knowledge of the MIMO channel. U.S. Pat. No. 8,073,069, hereby incorporated by reference in its entirety, describes a MIMO downlink beamforming system. For achieving receive diversity, it has been described that the receiver can use linear combining schemes such as maximal-ratio combining (MRC), equal-gain combining (EGC) and optimum combining which also require complete or partial channel state information (CSI) for decoding of the data. For estimation of the channel gains at the receiver, a training overhead is required which leads to the wastage of valuable bandwidth. In MIMO systems, the training overhead reduces the effective data rate significantly. Moreover, perfectly feeding back the exact values of the channel coefficients from the receiver to the transmitter is a challenging task since it requires a fast feedback link with very large bandwidth. Inaccurate or outdated channel values at the transmitter have the potential to destroy the transmit diversity.
Use of deterministic weights at the transmitter or at the receiver works for a channel with a non-zero mean or fixed component resulting in a finite K-factor, such as a Ricean channel and has been described in M. Vu and A. J. Paulraj, “Optimum space-time transmission for a high K factor wireless channel with partial channel knowledge,” Wireless Commun. Mob. Comput., vol. 4, pp. 807-816, November 2004. Capacity optimizing transmission schemes with deterministic weights have been described for the case of Ricean fading, as in M. Vu and A. Paulraj, “On the capacity of MIMO wireless channels with dynamic CSA,” IEEE Sel. Areas Commun., vol. 25, no. 7, pp. 1269-1283, September 2007; and M. Vu and A. J. Paulraj, “Optimum space-time transmission for a high K factor wireless channel with partial channel knowledge,” Wireless Commun. Mob. Comput., vol. 4, pp. 807-816, November 2004. A modified maximum likelihood (ML) receiver based on deterministic combining is proposed in R. K. Mallik and J. H. Winters “Deterministic combining for fading channels,” in Conf. Rec. IEEE International Conference on Communications (IC(:), Dresden, Germany, June 2009, pp. 1-5, for single-input multiple-output (SIMO) communications systems.
It is desirable to provide a MIMO system in which the transmitter and the receiver utilize only the knowledge of the channel statistics for deterministic array and receiver processing.